Method of controlling electrostatic charges on moving surfaces



Nov. 25,1930. w. H. CHAPMAN 1,782,712-

METHOD OF CONTROLLING ELECTROSTATIC CHARGES ON MOVING SURFACES FiledJan. ll 1930 6 I Q 0 F 4 mlfi g9 Inventor mIlzam/Empuzan Patented Nov.25, 1930 UNITED STATES PATENT OFFICE WILLIAM HENRY CHAPMAN, OF PORTLAND,MAINE, ASSIGNOR T C HAPIEAN ELEC- TRIC NEUTRALIZER COMPANY, OF PORTLAND,MAINE, A CORPORATION OF MAINE METHOD OF CONTROLLING ELECTROSTATICCHARGES ON MOVING SURFACES Application filed January 11, 1930. SerialNo. 420,058.

My present invention relates to the control of electro-static. chargeson a moving web of paper or fabric in the course of its manufacture orprinting and to a method of controlling the degree and character ofdischalrges such as are required forsuch contro In this art and underthe widely varying conditions and constructions of the apparatus used',it is' frequently difiicult, if not impossible, to locate the dischargebar at the point where the neutralization is desired. It sometimeshappens that after passing ;the neutralizer the sheet by reason of someinanipulation' takes on another charge and becomes diificult to handle.A characteristic instance of this is in printing presses with a flystick delivery. Here the paper having been neutralized picks up anothercharge in passing over the fly sticks and becomes difficult to handle.It is, of course, impossible to locate a bar close enough to the widelymoving fly sticks to neutralize the charge.

My present invention conceives of anticipating this difliculty byproviding for neutralizing the static charge before it is actually.

formed on the paper. In other words, it contemplates the application ofa high tension alternating charge of electricity in a manner to causethe reversal of the polarity of the initial charge on the paper so as tocounteract subsequent charges that may be generated on the paper afterit has reached any location that would be inaccessible for its directtreatment.

It also has for its object the application of the high tensionalternating charge of electricity in a manner to counteract the neg--ative charge normally produced on paper by an alternating charge whenthe paper is backed by a solid conducting substance at the pointoftreatment.

In my Patent No. 1,228,405,,1 announced the discovery of the negativecharging action of pointed conductors having alternating charges in themand showed how that action can be utilized for generating a very highvoltage charge of negative electricity on a moving web of paper. Thataction has al- Fig. 3 shows the factors adjusted to neu-- tralize, and

Fig. 4 shows a further adjustment for counteracting the negative chargethat would otherwise be generated where the paper has a solid substanceon the side of it opposite to the discharge points.

My present invention or discovery aifords a new basis of practice. It'aifords a definite control by which factors may be given new uses. 7

The use of an alternating current as a source of neutralizing dischargeas disclosed by me in 1904 and subsequently is of great efliciency inneutralization. 4

As heretofore disclosed, this has been effected by discharge pointseither connected directly to the source of alternating current or elsecapacitively coupled to it. My present method also may be practiced withdischarge points either connected directly or capacitively coupled withthe source of alternating current.

The factors involved in my method are only those heretofore usuallyemployed. The novel effects are attained by new methodical relations bywhich not only improved but new and definite results are made possible.

Considered broadly these are the electrical discharge upon the surfaceat a predetermined angle which is one factor of control and in relationto a ground factor which may be positioned relative to the axis ofdischarge and to the surface or body to be controlled.

There are, therefore, involved angles, po-

sitions, distances of separation, and as will be explained, correlatedand c'ombinative factors by which methodical procedure may be attained.

Where the sheets come from some operation, as that of a printing press,over a conveyor to fly sticks which deposit them in a stack on a table,there is an electrical charge developed by the printing press or otheragency and such charge may be either positive or negative according tocircumstances.

By way of illustration I have shown in Fig. 1 a somewhat diagrammaticview in which a distributor bar A is directly connected to a source ofhigh tension alternating current and the discharge points Dcapacitively. coupled with the bar. This. is preferable because itlimits the amountof shock that an operative can get by touching thepoints. The discharge points D, however, may be directly connected tothe bar although not so shown.

P indicates the plane of travel of the surface to be controlled.

G indicates a ground which may be and usually is in practice a definiteconductor such as abar usually of substantial diameter such asthree-eights or one-half inch.

These physical factors are to be understood as merel physical elementsbut their relationship w1ll be better understood by a diagrammaticconsideration 'of their functions.

To this end I have illustrated several characteristic situations.

For example, we may take a situation such as is indicated in Fig. 2. Inthis the paper or like material is previously charged with a minuscharge and is destined to arrive under the influence of a mechanicalfactor which will impart a new minus charge. My concept is to anticipateby reversal.

In accordance with my method I dispose the ground G toward the new chare producer or on that side of the discharg from the point D towardswhich the surface is moving.

The result of this is to neutralize the minus charge of the surface andat the same time to reverse it so that upon arrival under the influenceof X with its minus tendency the effect is neutralization.

If the influence X is not present reversal is not necessary. In Fig. 3,I illustrate the case of a minus charge neutralized butnot reversed. InFig. 4 I illustrate the case where there is a surface of solidconducting material immediately underneath the paper to be treated. Inthis case I place the ground G closely adjacent to the upper surface ofthe paper, preferably just in contact with it, and the discharge pointsD are directed so that the axial line of the point is approximatelytangent to that side of G toward ing. Under these conditions any chargeon the paper whether positive or negative be-'' comes neutralized andthe ordinary detrimental influence of the solid conducting sur- I faceunder the paper is counteracted.

My invention as herein disclosed may be variously practiced and is ofgeneral applicability as will be obviously to those skilled in this art.

What I therefore claim and desire to secure by Letters Patent is:

1. That method of attaining predetermined degrees and polarities in theneutralization of electric charges on moving surfaces which consists indirecting neutralizing discharges at a predetermined angle to thesurface in the direction of its movement and in maintaining a groundlaid transversely on one side or the other of the line of discharge toeffect the desired polarity and at a predetermined distance from thesurface to control the degree.

2. That method of attaining predetermined degrees and polarities in'theneutralization of electric charges on moving surfaces which consists indirecting neutralizing discharges coming from a capacitively coupledconductor at a predetermined angle to the surface in the direction ofits movement and in maintaining a ground laid transversely on one sideor the other of the line of discharge to effect the desired polarity andat a predetermined distance from the surface to control the degree.

3. That method of attaining predetermined clegrees and polarities in theneutralization of electric charges on moving surfaces which consists indirecting neutralizing discharges at a predetermined angle to thesurface in the direction of its movement and relative to a ground laidtransversely of the surface and positioned at that side of the line ofdischarge controlling the desired polarity and at a predetermineddistance from the surface to control the degree.

4. That method of attaining predeter-- mined degrees and polarities inthe-neutralization of electric charges on moving surfaces which consistsin directing neutralizing discharges coming from a capacitively coupledconductor at a predetermined angle to the surface in the direction ofits movement ar '1 relative to a ground laid transversely of the surfaceand positioned at that side of the line of discharge controlling thedesired polarity and at a predetermined distance from the surface tocontrol the degree.

5. That method of effecting the neutralization of electric charges onmoving sheets which consists in producing a reversal of the polarity ofthe preceding charge upon the paper to a degree which will neutralize asucceeding charge formed on the sheet after it has passed theneutra-lizer.

6. That method of efiecting the neutralization of electric charges onmoving sheets which consists in producing a reversal of the polarity ofthe preceding charge bydischarging upon the sheet in the direction ofits motion to a degree which will neutralize a succeeding charge formedon the sheet after it has passed the neutralizer. I

In testimony whereof I aflix my signature.

WILLIAM HENRY CHAPMAN.

